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Full text of "Text Book Of Mechanical Engineering"

.508                            Square Shafts.

w being exerted through 2?r feet at every revolution:

rT ^

H.P.=

X 27T N

s 7T ^8        27T N

x

-
33000       12x16     33000     320^10

_..

= ^320810

_    __
tJ   p

.:

68-44

J.

H.P.

V7VN

Example 47.A shaft transmits 20 H.P. at 160 revs. Find (i)
how many H.P. it will transmit at 250 revs., and (2) dia. to transmit
40 H. P. at 250 revs, withy at 2 tons per sq. in. for stiffness.

(0

(2),

H.P. ex

/.    20 oc loo   and    H, P. req. a 250
100 : 20 : : 250 : H. P.   and H. P. = 50

d= 68'44

40

2x2240x250

=2-215

Ex-ample 48. Compare the weight of shafting in a twin with that
iri a single screw ship, neglecting couplings: the H.P. in each being
the same and the speed of each twin being 25 /e above that of the
single screw. (Hons. Mach, Constr, Ex., 1886.)

d oc

_

"H   P

'

... a i for single shaft ... oc      73 for each twin shaft.

-  i for single shaft ... 

screws.

Square Shafts are often adopted in travelling cranes. In
Fig. 490, B Is the longitudinal and A the CTOSS girder of a crane,
the power being given from shaft D through mitre gear to F, and
by spur gear to G. As the carriage moves along B, the tumbler
bearings are turned through a right angle, and are only off the
shaft during the passage of the rnitre wheels, the bracket at B
being shaped to serve as a tappet.